Product and process trimerization of organic isocyanates

ABSTRACT

Disclosed is a method for the trimerization of organic isocyanates comprising thermally activating, in the presence of said isocyanates, a catalyst comprising a carboxylic acid salt selected from the alkali metal salts or quaternary ammonium salts of particular substituted malonic acids or half-esters thereof, particular carbamyl substituted aliphatic acids, or triaryl acetic acids. 
     Mixtures of the catalysts with isocyanates have surprisingly long periods of stability at ambient temperatures (about 20° C.) which makes the present method particularly suitable to systems for molding polyiso-cyanurates wherein long open times are required of a resin pre-mix prior to the actual curing step.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for polymerizing organic isocyanatesand is more particularly concerned with a process for trimerizingisocyanates in the presence of thermally activable catalysts and withnovel catalysts therefor.

2. Description of the Prior Art

The polymerization of organic isocyanates and particularlypolyisocyanates to form either cellular or solid polyisocyanurates iswell known in the art. A large number and variety of trimerizationcatalysts have been disclosed in the prior art; see for example Saundersand Frisch Polyurethanes: Chemistry and Technology Part I, 1962, p 212,Interscience Publishers, New York, N.Y.

Quaternary ammonium salts and alkali metal salts of organic carboxylicacids have long been recognized as isocyanate trimerization catalysts.British Pat. No. 908,337 discloses both types of catalysts. U.S. Pat.No. 3,980,594 discloses particularly active quaternary ammonium salts.

U.S. Pat. No. 3,954,684 discloses effective trimerization catalystcombinations of tertiary amines with particular quaternary ammoniumsalts. Bis-quaternary ammonium salts have been disclosed aspolyisocyanurate forming catalysts in U.S. Pat. No. 4,186,255.

In the art of isocyanate trimerization there has always been a need fordelayed action or thermally activable catalysts. Generally speaking, theprior art catalysts are not useful in this regard because theirproperties have been directed at the opposite end of the scale, that isinitiating the trimerization reaction at as low a temperature aspossible.

It has now been discovered that a certain class of carboxylic acidsalts, some of which are believed to be novel compounds, behave asthermally activable catalysts for trimerizing organic isocyanates. Incontrast to prior art catalysts of the type referred to hereinbefore,the present catalysts can be premixed with the isocyanates at ambienttemperature (about 20° C.), and, in the absence of heat, are stable assuch for literally hours before polymerization of the isocyanateinitiates.

SUMMARY OF THE INVENTION

This invention comprises a method for the trimerization of an organicisocyanate comprising thermally activating in the presence of saidisocyanate a catalyst comprising a carboxylic acid salt selected fromthe group consisting of the following formulae: ##STR1## wherein R¹ in(I) is alkyl having 2 to 8 carbon atoms, inclusive, and each R¹ in (II)is independently selected from alkyl having 2 to 8 carbon atoms,inclusive, R² is a highly branched alkyl having 3 to 8 carbon atoms,inclusive, R³ is selected from the group consisting of hydrogen, alkyl,and aryl, R⁴ is selected from the group consisting of alkyl, aryl,aralkyl, and cycloalkyl, each R⁵ is independently selected from aryl,and M.sup.⊕ is a cation selected from the group consisting of alkalimetal cations and quaternary ammonium cation having the formula .sup.⊕N(R⁶)₄ wherein each one of the four R⁶ radicals is independentlyselected from the group consisting of alkyl, aralkyl, cycloalkyl, andradicals having the formula ##STR2## wherein R⁷ is selected from thegroup consisting of hydrogen and methyl and n is a number of from 1 to 4provided that no more than one R⁶ radical has the formula (IV).

This invention also comprises thermally activable organic isocyanatetrimerization catalysts comprising carboxylic acid salts selected fromthe salts (I), (II), and (III) above wherein M.sup.⊕ has the formulae.sup.⊕ N(R⁶)₄ and designated (Ia), (IIa), and (IIIa) respectively and R⁶is defined above.

Illustrative of the term "alkyl having 2 to 8 carbon atoms", inclusive,are ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and isomericforms thereof.

The term "highly branched alkyl having 3 to 8 carbon atoms" means analkyl radical in which the valency bond is attached to a secondarycarbon atom of said radical, such as isopropyl, isobutyl, 1-ethylpropyl,1-methylbutyl, 1-methylpentyl, 1-ethylbutyl, 1-ethylpentyl,1-methylhexyl, 1-methylheptyl, 1-ethylhexyl, 2-methylpropyl,2-methylbutyl, 2-methylpentyl, 2-methylhexyl, 2-methylheptyl,2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, and the like.

The term "alkyl" has the same meaning as alkyl having 2 to 8 carbonatoms set forth above but also including 1 carbon atom, i.e. methyl.

The term "aryl" means the radical obtained by removing one nuclearhydrogen atom from an aromatic hydrocarbon having 6 to 10 carbon atoms,and is inclusive of phenyl, tolyl, xylyl, naphthyl, and the like.

The term "aralkyl" means the monovalent radical obtained by removing onehydrogen atom from the alkyl portion of an aromatic alkane hydrocarbonhaving 7 to 18 carbon atoms, such as benzyl, phenethyl, phenylpropyl,benzhydryl, naphthylmethyl, and the like.

The term "cycloalkyl" means cycloalkyl having 4 to 6 ring carbon atoms,inclusive, such as cyclobutyl, cyclopentyl, cyclohexyl, and the like.

The term "alkali metal cation" means Na⁺, K⁺, and Li⁺.

DETAILED DESCRIPTION OF THE INVENTION

Generally speaking, there are many types of systems involving thetrimerization of organic isocyanates, particularly polyisocyanates, and,more particularly, aromatic polyisocyanates which can be employed in theprocess in accordance with the present invention. Typical, but notlimiting thereof, are the systems for formation of polyisocyanurates perse, polyisocyanurate-polycarbodiimides, polyisocyanurate-polyurethanes,polyisocyanurate-polyurethanes-polyureas,polyisocyanurate-polyamide-polyurethanes, etc. That is to say that, inaddition to the trimerization process in accordance with the presentinvention, other polymer forming ingredients or catalysts can be presentto form the corresponding copolymers. For example, carbodiimide-formingcatalysts and/or carbodiimide-containing polyisocyanates can be employedin combination with the present process. Organic polyols can be includedin the present process to form polyisocyanurate-polyurethanes. Amineextenders can be included to form the polyurea linkages. Andketene-aminal reactants can be included with polyols to form thepolyisocyanurate-polyamide-polyurethanes. For illustrative and detailedteaching in regard to the preparation of the above types ofpolyisocyanate based polymer systems including reactants and preparativeprocedures, reference is made to U.S. Pat. Nos. 2,993,870; 3,657,161;3,896,052; 3,899,443; 3,903,018; 4,296,212 and 4,342,841 whosedisclosures relative thereto and hereby incorporated herein byreference.

Generally speaking, when preparing polyisocyanurates in accordance withthe present process, in the absence of other catalysts and polymerforming ingredients such as polyols, a minor amount of polycarbodiimideformation takes place. The actual amount, of absence thereof, ofcarbodiimide formation depends largely on the activation temperatureemployed but, more importantly, on the presence or absence of otherreactants for the isocyanate. When other polymer forming ingredients arepresent such as organic polyols to form the polyurethanes, thencarbodiimide formation is minimal and sometimes cannot be observed atall.

In carrying out the process in accordance with the present invention, itwill be understood by those skilled in the art that it is not limited tothe preparation of non-cellular solid products but can also be used inthe preparation of cellular products. However, it is in the preparationof the former products wherein the greatest utility resides because ofthe thermally activable nature of the catalyst. The isocyanate andcatalyst can be premixed together with other components and handled as aone-component system which can be stored, pumped, cast, used toimpregnate other materials, etc., and then thermally activated to curequickly to the finished polymerized state.

Accordingly, the present process can be employed in the preparation ofsolid polyisocyanurates and related copolymers by such methods ascasting or molding, see U.S. Pat. No. 4,251,428 whose disclosurerelative to casting is hereby incorporated herein by reference; by resintransfer molding (RTM), see Reinforcement Role in the Resin TransferMolding Process and Comparison with Other Competitive Processes by S.Bernardini, pp 1 to 6 Section 15F, SPI pre-prints, 35th Annual TechnicalConference 1980, Reinforced Plastics Composite Institute, SPI whosedisclosure relative to RTM is hereby incorporated herein by reference;by pultrusion which involves resin-impregnated strands of roving pulledthrough an orifice of a die, and then through a heating chamber to curethe resin, see Process and Economic Factors for Pultrusion by J. A.Rolston, pp 1 to 5 Section 8G, Technical Proceedings 33rd AnnualConference Reinforced Plastics, February 1978, SPI whose disclosurerelative to pultrusion procedures is hereby incorporated herein byreference; by thermoset injection molding of the reactants in accordancewith the present process in the form of either liquids, solids, or lowmolecular weight powders, see U.S. Pat. No. 4,119,594 whose disclosurerelative to thermoset injection molding is hereby incorporated herein byreference; by bulk or sheet molding methods (BMC and SMC), see U.S. Pat.No. 4,250,292 and Modern Plastics, January 1980, pp 56 to 59 whosedisclosure relative to BMC and SMC procedures are hereby incorporatedherein by reference; and by reaction injection molding (RIM) proceduresparticularly in combination with known prior art catalysts and otheringredients, see U.S. Pat. No. 4,218,543 and 4,321,333 whose disclosuresrelative thereto are hereby incorporated herein by reference.

The novelty in the present invention resides in the thermal activationof the carboxylic acid salt trimerization catalysts (I), (II), or (III)defined above in combination with the organic isocyanate to betrimerized.

Preferably, the thermally activable trimerization catalysts for use inthe present process are the novel compounds having the formulae (Ia),(IIa), and (IIIa) defined above and most preferred within this group arethe salts defined by formula (IIa).

In respect of the radicals R¹ preferred is alkyl having 2 to 4 carbonatoms.

In respect of R² preferred is isoalkyl having 3 to 4 carbon atoms.

In respect of R³ alkyl is preferred over hydrogen and aryl with alkyl of1 to 4 carbon atoms being preferred for the alkyl radical.

In respect of R⁴ aryl is the preferred radical class.

In respect of R⁵ phenyl is the preferred radical.

In respect of M.sup.⊕, the quaternary ammonium cations otherwiseidentified as .sup.⊕ N(R⁶)₄ herein are preferred as a class with alkyland aralkyl radicals being preferred for R⁶ within this class.

Illustrative of the carboxylic acid salts for use in accordance with thepresent invention are the following, α-ethyl-α-isopropylmalonic acidmono-sodium salt, α-ethyl-α-isopropylmalonic acid mono-potassium salt,α-ethyl-α-isopropylmalonic acid mono-lithium salt,α-ethyl-α-isopropylmalonic acid mono-tetramethylammonium salt,α-ethyl-α-isopropylmalonic acid mono-tetraethylammonium salt,α-ethyl-α-isopropylmalonic acid monotrimethylbenzylammonium salt,α-ethyl-α-isopropylmalonic acid mono-trimethyl(2-hydroxypropyl)ammoniumsalt, α-ethyl-α-isobutylmalonic acid mono-potassium salt,α-ethyl-α-isobutylmalonic acid mono-tetramethylammonium salt,α-ethyl-α-isobutylmalonic acid mono-trimethylbenzylammonium salt,α-propyl-α-isobutylmalonic acid mono-trimethylbenzylammonium salt, andthe like; ethyl α-ethyl-α-isobutylmalonate mono-potassium salt, ethylα-ethyl-α-isobutylmalonate mono-trimethylbenzylammonium salt, ethylα-ethyl-α-isobutylmalonate mono-trimethyl(2-hydroxypropyl)ammonium salt,butyl α-ethyl-α-isobutylmalonate mono-potassium salt, butylα-ethyl-α-isobutylmalonate mono-trimethylbenzylammonium salt, butylα-butyl-α-isopropylmalonate mono-potassium salt, butylα-butyl-α-isopropylmalonate mono-trimethylbenzylammonium salt, and thelike; potassium 2-ethyl-2-[(methylamino)carbonyl]butanoate,trimethylbenzylammonium 2-ethyl-2-[(ethylamino)carbonyl)]butanoate,trimethylbenzylammonium 2-ethyl-2-[(butylamino)carbonyl]butanoate,trimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]butanoate,tetramethylammonium 2-ethyl-2-[(phenylamino)carbonyl]butanoate,trimethyl(2-hydroxypropyl)ammonium-2-ethyl-2-[(phenylamino)carbonyl]butanoate,trimethylbenzylammonium 2-ethyl-2-[(benzylamino)carbonyl]butanoate,trimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]hexanoate,trimethylbenzylammonium 2-ethyl-2-[(cyclohexylamino)carbonyl]butanoate,and the like; sodium triphenylacetate, potassium triphenylacetate,lithium triphenylacetate, tetramethylammonium triphenylacetate,trimethylbenzylammonium triphenylacetate, and the like.

Preferred carboxylic acid salts in accordance with the present inventionare α-ethyl-α-isobutylmalonic acid mono-trimethylbenzylammonium salt,ethyl α-ethyl-α-isobutylmalonate mono-trimethylbenzylammonium salt,trimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]butanoate,potassium 2-ethyl-2-[(phenylamino)carbonyl]hexanoate,trimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]hexanoate, andtrimethylbenzylammonium triphenylacetate.

The carboxylic acid salt catalysts can be added to the isocyanate in anyconvenient manner depending only on the particular application beingemployed, the presence or absence of other ingredients, and the like.The catalyst can be employed in pure form, or, preferably, diluted witha diluent such as methanol, ethanol, ethylene glycol, diethylene glycol,and the like. The catalyst can be added directly to the isocyanate, or,if preferred, it can be added to the reaction mixed with anotheringredient such as an organic polyol, and the like.

Generally speaking, the quantity of catalyst to be employed will varyaccording to factors such as the activity of a particularisocyanate-catalyst combination and the temperature (discussed below)which one chooses as the activation and/or curing temperature for agiven system, that is to say, the temperature at which the isocyanatepolymerizes rapidly to the polyisocyanurate. However, the optimum amountis easily determined for any system by a process of trial and error.

Advantageously, the catalyst is employed in an amount falling within arange of from about 0.05 to about 10 mole percent, preferably from about0.1 to about 2 mole percent per mole of isocyanate being trimerized.

The terms "thermally activating" and "thermally activable" as usedherein mean heating above ambient room temperature (about 20° C.) andbecoming active above ambient temperature respectively.

Generally speaking, the process in accordance with the present inventionis amenable to any elevated temperature which provides reasonably shortcure times or reaction rates. Advantageously, the reaction mixture beingemployed is heated to a temperature falling within a range of from about50° C. to about 200° C., and, preferably from about 60° C. to about 150°C.

Trimerization catalysts, including those in accordance with the presentinvention, are characterized by a finite induction period when measuredat about 20° C. in the absence of solvents before the trimerizationreaction initiates. Additionally, for any given catalyst the rate atwhich the cure or completion of the trimerization proceeds afterinitiation will vary. Generally speaking, prior art catalysts haveinduction times which measure in minutes, for example less than 1 hourand more often about 2 to about 30 minutes.

Contrastingly, catalysts in accordance with the present invention, underthe same test conditions (i.e. about 20° C. and in the absence ofsolvent), have induction times greater than 1 hour.

A very surprising, and most useful, feature of the process in accordancewith the present invention is the prolonged stability of theisocyanate-catalyst system at ambient temperatures coupled with the veryrapid completion of the trimerization process once the system has beenthermally activated. Generally speaking, once the trimerization processinitiates, its completion is a matter of seconds to minutes depending onthe particular polymer system and on the activation temperature beingemployed. It is this particular feature that makes the present processso adaptable and useful in the various molding and preparativeprocedures set forth above.

It will be obvious to one skilled in the art that the catalysts inaccordance with the present invention may be employed in systems whichcall for the use of a solvent. However, in this connection, dependingupon the particular solvent employed, the induction times will vary fromthose values set forth above. The preferred embodiments of the presentprocess are those which are carried out in the absence of solvent.

Both the known and novel carboxylic acid salts to be used in accordancewith the present invention are readily obtained using standardpreparative methods well known to those skilled in the art. Thefollowing schematic equation represents a general preparative procedurewherein a carboxy functional compound (V) is reacted with slightly lessthan one molar equivalent of a reactant (VI) to produce a carboxylicsalt corresponding to any one of formulae (I) through (III) and (Ia)through (IIIa), inclusive ##STR3## wherein R⁸ represents the molecularresidues of any one of (I) through (III) after removal of thecarboxylate moiety, M represents the neutralized forms of the alkalimetal cations and quaternary ammonium cations defined above, and Atypically represents a neutralized anion such as hydroxyl, hydride,alkoxide, and the like. The reactant (VI) is used in slightly less thanmolar equivalency to insure that no residual (VI) will remain in theproducts because these reagents, for the most part, are strongtrimerization catalysts in their own right.

When M represents sodium, potassium or lithium and A is hydroxyl thenthe reaction is a simple neutralization reaction between the base (VI)and acid (V).

Alternatively, sodium, potassium, or lithium alkoxides such as sodiummethoxide or exthoxide can be used to neutralize the acid.

Preferably, a quaternary ammonium hydroxide is used to neutralize theacid and this can be typically carried out in alcoholic solution (suchas methanol). The neutralization is preferably carried out by adding asolution of the acid to a solution of the quaternary ammonium hydroxidecontaining an acid-base indicator. The neutralization is taken just tothe acid side to insure that no quaternary ammonium hydroxide remains.The solution containing the carboxylic acid salt can be used as suchwithout purification, or alternatively, can be concentrated by knownmethods to remove solvent from the active ingredient; see U.S. Pat. No.3,954,684 cited supra for teaching related to the preparation ofquaternary ammonium salts and which disclosure is incorporated herein byreference.

In the event that R⁸ in the reactant (V) is the residue corresponding to(I) in which R³ is hydrogen, then the neutralization is just carriedover to the acid side to further insure that the di-salt is not formed.The catalysts in accordance with the present invention while including afree carboxylic acid group in the same carboxylic salt molecule, do notinclude the di-salt form in the same molecule. The reason for this isthe fact that the di-salts do not have the same characteristicallydelayed onset of the trimerization reaction as the mono salts inaccordance with the present invention.

The starting carboxylic acids are, for the most part, commerciallyavailable or else known compounds which are easily prepared. The malonicacids, and half-esters, and triaryl acetic acids, corresponding toformulae (I) and (III) are known compounds; for teaching directed topreparation of mono anilides, mono amides, etc. of malonic acids (II)see Acta. Acad. Abo. Math. Phys. 1969, 29(8), 13 (Chem. Abstracts 73,45407m).

The isocyanates to be used in accordance with the present invention canbe any of the organic isocyanates, particularly organic polyisocyanates,and, preferably, aromatic polyisocyanates known to those skilled in theart which are referred to in the patents cited supra.

Typical, but not limiting, of the isocyanates which can be used arephenyl isocyanate, hexamethylene diisocyanate, 4,4'-methylenebis(phenylisocyanate), m- and p-phenylene diisocyanate, 2,4- and 2,6-toluenediisocyanate and mixtures of the 2,4- and 2,6-isomers,polymethylenepolyphenyl isocyanates, the various types of liquefiedmethylenebis(phenyl isocyanates) obtained by reacting themethylenebis(phenyl isocyanate) in varying proportions with minoramounts of one or more glycols and the liquid diisocyanates comprisingthe carbodiimide-containing methylenebis(phenyl isocyanates) having anisocyanate equivalent weight of from about 130 to about 180. Alsoincluded within the scope of the present invention are isocyanateterminated polyurethane prepolymers.

Preferred amongst the typical species cited above are the aromaticpolyisocyanates.

Any of the polyisocyanates, polyols, difunctional extenders in thereferences cited supra can be employed in the present process. Apreferred process comprises the trimerization of an aromaticpolyisocyanate in the presence of an organic polyol.

Other optional additives such as dispersing agents, cell stabilizers,mold release agents, surfactants, flame retardants, colorants, and thelike can be added to the trimerization process in accordance with thepresent invention.

The delayed action of the present catalysts which can be activated atrelatively low temperatures makes the present process particularlysuitable to those preparative methods which call for the use of onecomponent systems that must be premixed, manipulated, and otherwisehandled before the final curing step. This is particularly true in thosecases where reinforcing fibers, roving, fiber bundles, mats, etc., mustbe thoroughly impregnated with a resin system prior to polymerization ofthe resin. Accordingly, this is why the present process is applicable toBMC, RTM, and pultrusion processes referred to hereinbefore.

Accordingly, the process for making polyisocyanurate articles inaccordance with the present invention is useful, inter alia, for thepreparation of molded solid cast elastomers, elastoplastics, and thelike. Such molded products find particular utility as auto parts such ascar bumpers, body elements, panels, doors, engine hoods, skirts, airscoops, and the like. Further, the good high temperature resistance ofsuch polyisocyanurate containing articles makes them eminently suitablewhere higher than normal temperature resistance is required.

The following examples describe the manner and process of making andusing the invention and set forth the best mode contemplated by theinventor of carrying out the invention but are not to be construed aslimiting.

EXAMPLE 1

(a) A 50 g. sample of 40 percent by weight of trimethylbenzylammoniumhydroxide in methanol was placed in a 250 ml. breaker and a crystal ofbromothymol blue indicator dissolved therein.

There was slowly added to the beaker with constant stirring, ethylα-ethyl-α-isobutylmalonate monocarboxylic acid until the color of thesolution just turned to yellow (pH=about 6.0).

Thus there was produced ethyl α-ethyl-α-isobutylmalonate monotrimethylbenzylammonium salt in accordance with the present inventionhaving the following formula in accordance with (Ia) above ##STR4## andin the form of a solution of about 57.6 percent by weight in methanoland the water formed by the neutralization.

(b) Using the same procedure and ingredients as described above exceptthat α-ethyl-α-isobutylmalonic acid was added instead, until the colorof the solution just turned to yellow, there was producedα-ethyl-α-isobutylmalonic acid mono trimethylbenzylammonium salt inaccordance with the present invention having the following formula inaccordance with (Ia) above ##STR5## and in the form of a solution ofabout 55.7 percent by weight in methanol and the water formed by theneutralization.

(c) Using the same procedure and ingredients as described above exceptthat 2-ethyl-2-[(phenylamino)carbonyl]butanoic acid was added instead,until the color of the solution just turned yellow there was producedtrimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]butanoate inaccordance with the present invention having the following formula inaccordance with (IIa) above ##STR6## and in the form of a solution ofabout 58.9 percent by weight in methanol and the water formed by theneutralization.

(d) Using the same procedure and ingredients as described above exceptthat 2-ethyl-2-[(phenylamino)carbonyl]hexanoic acid was added instead,until the color of the solution just turned yellow there was producedtrimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]hexanoate inaccordance with the present invention having the following formula inaccordance with (IIa) above ##STR7## and in the form of a solution ofabout 60.5 percent by weight in methanol and the water formed by theneutralization.

The solution was concentrated in a rotary evaporator at a temperature ofabout 40° to 50° C. under a pressure of about 15 mm. of mercury toprovide a solution of about 85 percent by weight of the salt.

(e) Using the same procedure and ingredients as described above exceptthat triphenylacetic acid was added instead, and, heating the methanolsolution to facilitate dissolution of the acid, there was producedtrimethylbenzylammonium triphenylacetate in accordance with the presentinvention having the following formula in accordance with (IIIa) above##STR8## and in the form of a solution of about 61.9 percent by weightin methanol and the water formed by the neutralization.

The solution upon standing precipitated some free acid and the solutioncolor turned to green indicating a shift in equilibrium back to freeacid and its precipitation. However, upon slight warming the solidredissolved and the solution regained its yellow neutral color.

EXAMPLE 2

The following data in Table I sets forth a comparison of reactivities ofa number of trimerization catalysts to be used in accordance with thepresent invention (Runs 1, 2, 6, 7, 8 and 11) with catalysts not inaccordance with the present invention (Runs 3 to 5, 9, 10 and 12 to 14).The reactivity being measured was the elapsed time between mixing thecatalyst with an isocyanate and the initiation of the trimerizationreaction. The catalysts used in accordance with the present process werethe (1a) to (1e) samples set forth in Example 1, and potassium2-ethyl-2-[(phenylamino)carbonyl]hexanoate. In Run 15 trimerizationreactions in accordance with the present invention were carried outusing catalyst (1d) at four different activation temperatures.

A standardized procedure was employed throughout the runs wherein a 3 g.sample of purified (distilled) phenyl isocyanate was placed in a smallglass jar followed by the specified catalyst at a concentration of about0.2 mole percent based on the isocyanate. The liquid ingredients werestirred thoroughly with a stirring rod and allowed to stand at roomtemperature (about 20° C.) and observed for any signs of reaction.

For the catalysts not in accordance with the invention, the times inwhich the trimerization initiated after mixing were all in a matter ofminutes. At the specified times, the liquid began to slowly exothermwith the exotherm temperature varying according to the catalyst employedfollowed by the solidification of the phenyl isocyanate to triphenylisocyanurate the structure of which was confirmed by nuclear magneticresonance spectrum analysis.

For the catalysts in accordance with the invention, induction timesgreater than 1 hour were observed and at the times specified thetrimerization reaction initiated in a matter of seconds with an exothermtemperature reaching 160° C. at times and followed by almost immediatesolidificaton of the mixture to triphenyl isocyanurate.

Runs 3 to 5 can be compared to Run 1 or 2 because the catalysts in theformer runs are closely related to those in 1 and 2. It is noteworthythat by simply varying the catalyst to have only straight chain alkylsubstituents (Run 3), the di-salt (Run 4), or a di-salt in accordancewith U.S. Pat. No. 4,186,255 (Run 5), the induction times are reduced tolevels well below those called for by the present process.

Similarly, the catalysts in Runs 9 and 10 are related in structure tothose of Runs 6, 7, 8 but show a vastly different reaction profile fromone group to the other.

Also, in the same ways Runs 12 to 14 are related to Run 11 but again avastly different reaction profile was observed.

Using the same procedure outlined above for the test comparisons, Run 15consisted of four seperate samples of phenyl isocyanate each of whichwere prepared with the catalyst (1d) at the 0.2 mole percent level. Eachjar containing the ingredients was placed in an oil bath which washeated to the temperature specified in Table I while the contents werestirred with a thermometer. The time was recorded when trimerizationinitiated after the ingredients had reached the respective bathtemperature. The reactions in all cases were very rapid with immediateexotherms to about 160° C. and almost immediate solidification of phenylisocyanate to the phenyl isocyanurate trimer.

                  TABLE I                                                         ______________________________________                                        Run No.                                                                              Catalyst          Induction Time                                       ______________________________________                                        1      1a                >8     hours                                         2      1b                2.5    hours                                         3      α,α-diethylmalonic acid                                                             25     minutes                                              mono trimethylbenzyl-                                                         ammonium salt                                                          4      α,α-diethylmalonic acid di-                                                         10     minutes                                              [trimethylbenzylammonium                                                      salt]                                                                  5      α,α-diethylmalonic acid di-                                                         2      minutes                                              [triethyl-(2-hydroxypropyl)                                                   ammonium salt]                                                         6      1c                >8     hours                                         7      1d                >8     hours                                         8      potassium 2-ethyl-2-[(phenyl-                                                                   >4     hours                                                amino)carbonyl]hexanoate                                               9      trimethylbenzylammonium 2-                                                                      5      minutes                                              ethyl-2-[(phenylamino)car-                                                    bonyl]monothio-hexanoate                                               10     trimethylbenzylammonium 2-                                                                      20     minutes                                              methyl-2-[(dodecylamino)                                                      carbonyl]propionate                                                    11     1e                4      hours                                         12     trimethylbenzylammonium                                                                         2      minutes                                              2-ethyl-hexanoate                                                      13     trimethylbenzylammonium                                                                         9      minutes                                              2,2-dimethyloctanoate                                                  14     trimethylbenzylammonium                                                                         17     minutes                                              benzilate                                                              15     1d                30     seconds (100° C.)                                               3.5    minutes (80° C.)                                                11.25  minutes (65° C.)                                                41     minutes (55° C.)                       ______________________________________                                    

EXAMPLE 3

The following experiments set forth two trimerization reactions inaccordance with the present invention of a liquefied polyisocyanate, onein the absence, and, the second in the presence of an organic polyol.

The polyisocyanate was a modified liquid methylenebis(phenyl isocyanate)(MDI) obtained by treating an MDI comprised of about 94 percent byweight of the 4,4'-isomer and 6 percent of the 2,4-isomer in accordancewith U.S. Pat. No. 3,384,653 to form carbodiimide groups; I.E.=143.7.

In the first reaction, 100 g. of the above polyisocyanate was weighedinto an open aluminum pan and 1 g. of a methanolic solution oftrimethylbenzylammonium 2-ethyl-2-[(phenylamino)carbonyl]hexanoate(about 60.5 percent by weight) was thoroughly mixed in using athermometer as a stirrer. The temperature immediately rose from 20° C.to 25° C. and a very small amount of solids precipitated but neither thetemperature rose any more nor did any more solids precipitate. Thepolyisocyanate stood for about 6 hours and 5 minutes at 20° C. beforetrimerization began and the mixture thickened. The viscous plaquematerial was cured at 100° C. for 5 minutes causing a moderate amount offoaming which was due to the evolution of carbon dioxide frompolycarbodiimide formation.

In the second reaction, 144 g. of the above isocyanate was thoroughlyblended with 40 g. of a polyethyleneoxypolypropyleneoxy diol having anequivalent weight of 1000, and 1.8 g. of the catalyst solution. Theaddition of the catalyst caused an initial exotherm to 36° C. and aninitial viscosity increase both of which were believed to be due tourethane prepolymer formation. The system cooled back to 20° C. and wasstable for greater than seven hours. Two separate samples of the mixturewere cured, one at 100° C. in 3 minutes, and another at 150° C. in 2minutes to form two solid polyisocyanurate plaques with little to nofoaming observed. The polymer structure was confirmed by infraredanalysis showing the isocyanurate linkages in both cases.

EXAMPLE 4

The following four trimerization reactions were carried out similarly tothe above described experiments by weighing out samples of 3.0 g., 3.0g., 3.3 g., and 3.3 g. of phenyl isocyanate into four separate smallglass jars. The first jar was mixed with 1 drop of the methanolicsolution of trimethylbenzylammonium2-ethyl-2-[(phenylamino)carbonyl]butanoate (at about 60.5 percent byweight) and heated to 70° C. whereupon after 9 minutes the reactantturned solid in a few seconds.

To the second, third, and fourth jars there was added 0.6 g., 0.3 g.,and 0.1 g. respectively of the monoethylether of diethylene glycol alongwith 1 drop of the catalyst solution. The three jars were heated to 100°C. and after about 35 seconds their contents solidified.

Infrared analysis of the four solid samples showed that product from thefirst jar had the predominant absorption at 1700 cm⁻¹ for isocyanurategroups along with a minor absorption at 2130 and 2100 cm⁻¹ forcarbodiimide linkages. It should be noted that this infrared absorptionspectrum was virtually identical to the spectrum of the product from thesame reactants but heated to 100° C.

The second jar had no discernible carbodiimide linkages but onlyisocyanurate and urethane. The last two jars had only small amounts ofcarbodiimide detectable by infrared absorption.

The presence of hydroxyl groups to co-react with the isocyanateobviously suppresses the formation of carbodiimide.

In a similar experiment to the one described above but usingpolyfunctional ingredients, four samples of 5.4 g., 5.8 g., 5.6 g., and6.3 g., of pure 4,4'-methylenebis(phenyl isocyanate) were reacted at100° C. with 1.0 g., 2.0 g., 2.5 g., and 3.5 g. respectively of Poly G55-112 (a polyethyleneoxy-polypropyleneoxy diol of 500 hydroxyl eq. wt.;supplied by Olin Chemical Corp., New Haven, Conn.) in the presence of 2drops each of the above catalyst solution.

The first sample containing the 1 g. of polyol showed significantfoaming during the polymerization. Foaming was only borderline in thesecond sample. The third and fourth samples showed only slight bubbleformation in the final solidified polymer pieces with no appreciabledifference between the two.

In the absence of polyols, the polymer obtained was a polyisocyanuratecontaining a minor amount of polycarbodiimide whereas in the presence ofan appreciable polyol concentration the polycarbodiimide was not formedto any extent.

I claim:
 1. A method for the trimerization of an organic isocyanatecomprising thermally activating at a temperature of from about 50° C. toabout 200° C. in the presence of said isocyanate a catalyst otherwisehaving an induction period greater than one hour for initiating saidtrimerization at about 20° C. said catalyst consisting essentially of acompound selected from the group consisting of the following formulae##STR9## wherein R¹ in (I) is alkyl having 2 to 8 carbon atoms,inclusive, and each R¹ in (II) is independently selected from alkylhaving 2 to 8 carbon atoms, inclusive, R² is a highly branched alkylhaving 3 to 8 carbon atoms, inclusive, R³ is selected from the groupconsisting of hydrogen, alkyl, and aryl, R⁴ is selected from the groupconsisting of alkyl, aryl, aralkyl, and cycloalkyl, each R⁵ isindependently selected from aryl, and M.sup.⊕ is a cation selected fromthe group consisting of alkali metal cations and quaternary ammoniumcations having the formula .sup.⊕ N(R⁶)₄ wherein each of the four R⁶radicals is independently selected from the group consisting of alkyl,aralkyl, cycloalkyl, and radicals having the formula ##STR10## whereinR⁷ is selected from the group consisting of hydrogen and methyl and n isa number of from 1 to 4 provided that no more than one R⁶ radical hasthe formula (IV).
 2. A method according to claim 1 wherein said compoundhas the formula (I).
 3. A method according to claim 2 wherein saidcompound has the formula ##STR11##
 4. A method according to claim 1wherein said compound has the formula (II).
 5. A method according toclaim 4 wherein said compound has the formula ##STR12##
 6. A methodaccording to claim 4 wherein said compound has the formula ##STR13## 7.A method according to claim 4 wherein said compound has the formula##STR14##
 8. A method according to claim 1 wherein said compound has theformula (III).
 9. A method according to claim 8 wherein said compoundhas the formula ##STR15##
 10. A method according to claim 1 wherein saidisocyanate is an aromatic polyisocyanate.
 11. A method according toclaim 10 wherein said isocyanate is trimerized in the presence of anorganic polyol.
 12. A method for the trimerization of an aromaticpolyisocyanate in the presence of an organic polyol comprising heatingsaid polyisocyanate and said polyol at a temperature of from about 50°C. to about 200° C. in the presence of a catalyst consisting essentiallyof a compound in accordance with claim
 1. 13. A method according toclaim 12 wherein said compound has the formula ##STR16##